The four major components of a diesel engine are:

1. Cylinder block: This is the main structural component of the engine, which houses the cylinders and the pistons. The cylinder block is typically made of cast iron or aluminum alloy.
2. Piston and connecting rod: These components form the reciprocating assembly that converts the linear motion of the pistons into rotary motion. The pistons are typically made of aluminum alloy or cast iron and are connected to the connecting rod, which in turn is connected to the crankshaft.
3. Crankshaft: This is the main rotating component of the engine, which converts the linear motion of the pistons into rotary motion. The crankshaft is typically made of steel or cast iron and is supported by bearings.
4. Fuel injection system: This is the system that delivers fuel to the engine. In a diesel engine, the fuel is injected into the combustion chamber under high pressure, which helps to ensure that the fuel is atomized and fully mixed with the air. The fuel injection system typically includes a fuel pump, injectors, and a fuel filter.

Other components that make up a diesel engine include the cylinder head, camshaft, valve train, oil pump, cooling system, and exhaust system. These components work together to ensure proper operation of the engine, while also providing cooling, lubrication, and emission control.

Some additional details about the other components that make up a diesel engine:

1. Cylinder head: The cylinder head sits on top of the cylinder block and forms the combustion chamber. It contains the ports for the intake and exhaust valves, and also houses the spark plug (in the case of a gasoline engine) or pre-combustion chamber (in the case of a diesel engine). The cylinder head is typically made of cast iron or aluminum alloy and is sealed to the cylinder block using a gasket.
2. Camshaft: The camshaft is a rotating shaft that is driven by the crankshaft and controls the opening and closing of the valves. The camshaft is typically located in the cylinder head and is driven by a timing belt or a chain.
3. Valve train: The valve train consists of the valves, valve springs, rocker arms, and pushrods (or tappets) that open and close the valves to allow air and fuel into the engine and to remove the exhaust gases. The valve train is controlled by the camshaft and is typically located in the cylinder head.
4. Oil pump: The oil pump is responsible for pumping lubricating oil through the engine to lubricate and cool the moving parts. The oil pump is typically located in the oil pan and is driven by the crankshaft.
5. Cooling system: The cooling system is responsible for removing heat from the engine and maintaining the proper operating temperature. The cooling system typically includes a water pump, a radiator, and a thermostat.
6. Exhaust system: The exhaust system is responsible for removing the exhaust gases from the engine and reducing the emissions. The exhaust system typically includes an exhaust manifold, a catalytic converter, and a muffler.

These components, along with the main components like cylinder block, pistons, connecting rod, and crankshaft, work together to make the engine run efficiently, safely and comply with emissions standards.